This invention relates generally to ferroelectric materials, and specifically to ferroelectric systems for computing and data processing. In particular, the invention concerns a ferroelectric structure for use in non-volatile data storage systems and digital memory applications.
Non-volatile data systems span a range of different storage technologies, including disc drives, tape drives and other magnetic media-based systems. Non-volatile technologies are also used in flash drives and other addressable data storage arrays, including EEPROMs (electrically erasable programmable read-only memories) and other floating-gate transistor-based components. Ferroelectric materials in particular are utilized in a range of non-volatile random access memory (RAM) devices, including FRAM (or FeRAM) array-type components as well as probe-based devices utilizing a continuous ferroelectric medium.
In ferroelectric data storage systems, data are written by applying a write field (an electric field) to the ferroelectric material, such that the applied potential exceeds the ferroelectric coercive voltage. This causes the polarization to align along the write field direction. The polarization state is retained even after the write field is removed, making ferroelectric materials suitable for a range of non-volatile memory applications, as distinguished from standard volatile data systems such as DRAM (dynamic random access memory) and SRAM (static random access memory).
Transistor-based ferroelectric devices function similarly to flash memories, but have lower write field requirements and benefit from decreased power consumption and increased speed. Ferroelectric materials can also be used to manufacture continuous media, which function analogously to the magnetic media of traditional disc drives and tape-based data storage systems, but, depending upon material composition and manufacture, tend to have higher anisotropy energy and greater thermal stability, yielding high attainable storage densities with long data lifetimes.
Unfortunately, standard ferroelectric data storage systems require a destructive read cycle. In particular, ferroelectric memory is typically read out by generating a read voltage that exceeds the coercive voltage, in order to induce a switching signal when anti-aligned polarizations reorient along the read field. The switching signal (or lack thereof) defines a bit pattern, with “1” and “0” data states determined by the previously-written ferroelectric polarization, before the read potential was applied. At the end of the read cycle, however, each bit is oriented in the same direction as the read field; that is, the read process is destructive, such that the original data are erased, and will be lost unless a writeback loop or refreshing step is employed. As a result, there remains a continual need for improved ferroelectric data storage technologies, with particular respect to the problem of destructive data readback.